Hemopoiesis

WHAT IS HEMOPOIESIS?

Before we go further into hemopoiesis, let’s get to know general information about the components of blood in our body. There are more than 10 different types of cells in our body, which are categorized under 3 main categories, Red Blood Cells (also known as Erythrocytes). The second is White Blood Cell (also known as Leukocytes), and the last is Platelets (also known as Thrombocytes).


Thinglink. (n.d.). Composition of Blood. Www.thinglink.com. Retrieved October 2, 2022

‌Red blood cells contain the oxygen-carrying protein that is called hemoglobin. In the healthy adult male, they have about 5.4 million red blood cells per microliter of blood, while for a healthy adult female it is about 4.8 million. Red blood cells also are responsible for transporting oxygen because it has an internal space that is available for oxygen transport since they have no nucleus at all. 


Types of White Blood Cells (Leukocytes) with Functions and Picture. (2019, November 28). Science Facts. 


Besides, white blood cells (WBC), also known as leukocytes, are classified into granular and agranular. Granular contains granules that are visible by staining when seen using a light microscope. Under granular leukocytes, there are neutrophils, eosinophils, and basophils. In contrast, the agranular consists of lymphocytes and monocytes. Agranular also has cytoplasmic granules around the nucleus, but the granules are not visible under a light microscope because of their small size and poor staining qualities. 


Other than the immature cell types that develop into erythrocytes (red blood cells) and leukocytes (white blood cells), hemopoiesis also differentiates into cells that produce platelets. Platelets help stop blood loss from a damaged blood vessel by forming a platelet plug. 


Now we already recall the components of blood, so it will be easy to understand the process of hemopoiesis. Hemopoeisis is the formation of blood cellular components such as red blood cells, platelets, and others. Hemo means blood, and -poiesis means to make. Hemopoiesis is also known as haematopoiesis. Some of the blood may have a lifetime measured in years. Probably most formed elements of the blood only last hours, days, or weeks and must be restored frequently. In simple words, hemopoiesis is a process where the body creates and develops new blood cells from stem cells. This process occurs naturally in our body, and our body will continuously reproduce the blood cells through adulthood to keep the blood supply refilled. Scientists and researchers also study hemopoiesis to learn how blood disorders and cancers are formed and can be treated. Plus, do you know that the average amount of blood produced daily in human adults is 200 billion erythrocytes and 70 billion neutrophils? That is a lot. 


Therefore, there are three main points that will be explained later: the site where the hemopoiesis takes place, how the hemopoiesis happens, and the hemopoiesis impact on health. 



Where does hemopoiesis occur in the body?


Hemopoiesis occurs in many places. It is divided into two sites, extramedullary hemopoiesis and medullary hemopoiesis. Extramedullary means it happens outside of the bone marrow, while medullary means it happens inside the bone marrow. 


Print 2-Development-Embryonic Period flashcards - Easy Notecards. (n.d.). Www.easynotecards.com. Retrieved October 2, 2022


In the earliest stage, hemopoiesis occurs in the yolk sac when the fetus is 0-2 months. The yolk sac is a small membranous structure around the embryo. When the embryo continues to develop and reaches 2-7 months in the placenta, the site will automatically shift to the liver and spleen until 2 weeks after the fetus is born. Then during 5-9 months, the bone marrow becomes the primary source of blood cell production.  


Image result for skeleton structure. (n.d.). Pinterest. Retrieved October 2, 2022


After the baby is born, the development will occur in the bone marrow until adulthood. From birth to 3 years old, hemopoiesis takes place in the red bone marrow of almost every bone. In newborns, all the bone marrow is red and produces blood cells actively. Then, when the baby reaches 4 years old, the skeleton growth will exceed the red blood cell production demand. Thus, the hemopoiesis process will move to the axial skeleton, such as the flat bones, skull, ribs, sternum, clavicle, vertebrae, and pelvic, plus proximal ends of long bones, which are the humerus and femur. It will be completed by 18 years old. When people age, blood cell production will slowly decline, and the red bone marrow in the medullary cavity (bone marrow) becomes inactive. It will be replaced by the yellow bone marrow. The red bone marrow can transform the yellow bone marrow under specific circumstances, such as severe bleeding. Both red bone marrow and yellow bone marrow lie in bone marrow. Thus, yellow bone marrow is inactive and mainly composed of fat, while red bone marrow is actively producing the blood cells. 



How does hemopoiesis happen in our body?


Do you know that the rate of hemopoiesis depends on the body’s needs? The body will continuously produce new ones to replace the old ones. In fact, the body needs to replenish 1% of blood cells every day. As already mentioned before, all blood cells have different life spans. White blood cells have the shortest lifespan, while red blood cells can live only about 120 days. 


Production of the Formed Elements | Anatomy and Physiology II. (n.d.). Courses.lumenlearning.com. 


The process begins with the pluripotent stem cells. These cells have the capabilities to develop into many different types of cells. These cells will develop into two different types of stem cells which are myeloid stem cells and lymphoid stem cells. Myeloid stem cells are produced in the red bone marrow and form the erythrocytes (red blood cells), platelets, monocytes, neutrophils, eosinophils, basophils, and mast cells. Besides, the lymphoid stem cells will divide into B-cell, T-cell, and natural cell lymphocytes. Compared to white blood cells that produce from myeloid cells, these 3 cells have different functions for the human immune system. 


Myeloid cells, as mentioned, will produce red blood cells, white blood cells, and platelets. For your information, there are specific names for each process. For the production of red blood cells, it is called erythropoiesis. Erythro means red blood cell, and -poiesis is formation. So erythropoiesis is the formation of red blood cells. For white blood cells is called leukopoiesis, and its consists of three different types:

  1. Granulopoiesis - which produces neutrophil, eosinophil, and basophil

  2. Monopoiesis - produces monocytes

  3. Lymphopoiesis - produces B-cells and T-cells


And last is the formation of platelets or known as thrombopoiesis. So, during hemopoiesis, some of the myeloid cells and lymphoid cells will directly develop into precursor cells or known as blasts. In simple words, it already partially differentiates to form one type of mature blood cell. Then, over some cell divisions, they transform into the basic form of a blood cell, like we always learned before. For example, the precursor cell in monocytes is called monoblasts, which will develop into monocytes and become matured cells.



What disease might occur?


On the other hand, there are a few cases where extramedullary hemopoiesis (which happens outside the bone marrow) can occur in adults, which means the person might have the disease. The first case is where the bone marrow is no longer functional, so the liver will take the place of the bone marrow’s function. The second case is where the bone marrow, such as anemia, cannot keep up with the demand for blood cells. Anemia can cause you to feel weak and tired because your body does not get adequate oxygen supply from the red blood cells. Anemia also may occur when someone is getting older, and the number of fat increases in the bone marrow. So it will make blood cell production complex, and the body cannot produce extra blood cells if it needs them due to illness. Besides, if the person has inadequate white blood cells, it will risk the immune system's function to fight off an infection. And if the platelets amount is low, you might have a higher risk of bleeding excessively. 


webadmin. (n.d.). Neurological disorders. Cancer Pain-India. Retrieved October 2, 2022‌


Blood cancers such as lymphoma, leukemia, and myeloma can also lead to blood cell formation. But there is a hematologist who is a specialist in blood disorders. If someone has a disease with a condition related to hemopoiesis, there are treatment plans that can help to treat the disease. For example, leukemia can be treated with chemotherapy. The blood cell production may return to normal with proper treatment.


BY: NURIN AMALIA KAMARUL SAHRIN

Comments

Post a Comment

Popular posts from this blog

Erythropoiesis and Factors Affecting Erythropoiesis

Image
Erythropoiesis is the scientific term for the production of the red blood cells (erythrocytes) from the bone marrow called stem cells. Erythrocytes are vital for your health. They carry almost all the oxygen in your body which is used to make almost half of your blood. 8 out of 10 cells in your body are red blood cells. The marrow of certain bones constantly produces red blood cells. As noted previously, the marrow spaces of the vertebrae, ribs, breastbone, and pelvis are the primary sites of red cell generation, or erythropoiesis, in adults. The erythroblast, a nucleated cell that lacks hemoglobin, is the fundamental precursor from which the red blood cell is produced in the bone marrow. Bone marrow is the tissue in your bones that functions as the factory for producing blood cells. For starters, the bone marrow creates stem cells and then these stem cells will then develop into more specialized cells called Common myeloid progenitors (CMP) and has the ability to mature into all of th...
Read more

Iron Metabolism

Image
WHAT IS IRON METABOLISM? Di d you know that the usual iron intake is 10-20 mg per day for a person but the absorption is only 1-2 mg per day? Yes, it is that little! Iron can be obtained from the food we eat, such as meat and vegetables. Iron is an important element and is needed for the production of erythrocytes (erythropoiesis), as well as other important processes. It requires a tightly regulated process and takes place in the duodenum. In this article, we will go deeper about the process involved in iron metabolism which include iron absorption, transportation, and storage. From the diagram above, you can see the enterocyte. The left side is apical membrane and the other side is basolateral membrane. Let me tell you the process one by one so it will be easier to understand. When the iron intake is from the animal source like the meat we eat, which contains both haemoglobin and myoglobin, both of them contain heme. Inside the heme, there is iron. This iron which is in heme form is ...
Read more